Amal Carburetor Servicing Tip

Discussion in 'Motorbike Technical Discussion' started by Nomen Nescio, Sep 29, 2005.

  1. Nomen Nescio

    Nomen Nescio Guest

    Application: Twin cylinder, twin carburetor English bike equipped with
    Amals.

    Symptom: Will not tick over. Both cylinders fire reliably at 1500 rpm.
    Each plug can be grounded in turn and engine will run on either cylinder at
    1500 rpm or better. As throttle is backed off, one cylinder begins to
    misfire and the engine dies before idle speed is achieved.

    Turns out the problem is fuel starvation in the pilot (idle) circuit of one
    carburetor. Standard shop manuals do not eludicate the trouble. There is
    a fixed metering jet pressed into the bottom of the passage into which the
    air-adjustment screw is affixed. Remove the screw and shine a flashlight
    into the passageway to inspect the condition of the pilot jet orifice. It
    is very small in diameter and can be clogged by fuel deposits, especially
    if the bike has been sitting during winter. The orifice should appear as a
    tiny black spot. It is difficult to resolve the actual bore itself by eye.
    Test the fuel circuit by injecting some water into air-screw port and plug
    the air bleed at the carburetor bell end and apply a jet of compressed air
    at the air-screw port. Water should be ejected at the two fuel-air
    discharge ports in the venturi and, most importantly, water should be
    ejected from the fuel feed port of the carburetor body where it
    communicates to the fuel bowl. If water does not eject from any of the
    three ports, then that port or pilot jet is clogged.

    If the pilot jet cannot be opened by a soaking in carburetor cleaner and
    compressed air, it will be necessary to use a probe to push through the
    occulsion. Take a T-pin or a sewing needle and grind a slender taper to
    the end. Then insert this tool into the air-screw port, locate the center
    of the pilot jet and push the pin into the orifice to clear it. This
    repair procedure is not covered in shop manuals and this small pilot jet is
    overlooked in just about all cases, including, carburetor boil out
    servicing.

    These twins idle best with a rich mixture. One turn out from the seated
    position is about right. A rich mixture is a more powerful mixture because
    all the oxygen is consumed. A good engine should actually idle on one
    cylinder. Balance the mixture and idle speed such that each cylinder can
    sustain a minimum speed idle with the opposite cylinder grounded. Then with
    both cylinders firing, advance the idle speed screw of each the same amount
    to achieve a reliable 500 rpm idle. Expect under some conditions the idle
    to creep up to as high as 750 rpm. This variation is normal as the
    internal friction and atmospherics change the efficiency of the engine at
    idle. Given good compression, free clutch, good spark, correct timing,
    etc., weak mixtures are the major sources of complaints for difficult
    starting and idling.

    Given the lower fuel octane rating and conservative operation of the engine
    which limits these big twins to about 5500 rpm, there is a benefit in
    retarding the spark 6 degrees. The result will be a smoother, easier
    starting engine that will not ping under load using regular-grade gasoline.
     
    Nomen Nescio, Sep 29, 2005
    #1
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  2. Application: Newsgroup where motorbike riders with technical problems
    usually relating to older mass produced motorbikes seek solutions from
    other riders with cogent information about common problems.

    Problem: Anonymous user seeks to appear to be an expert on motobike
    technology, and posts answers to questions that were never asked.
    Information relates to motorbikes that most owners are unlikely to ever
    own or have problems with. Anonymous user seeks to turn technical
    discussions into abstruse debates in order to prove he's a genius in
    other areas too.

    Go away, Nomen Nescio.
     
    krusty kritter, Sep 29, 2005
    #2
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  3. Nomen Nescio

    Battleax Guest

    snip
    Hmmm...now that certainly sounds familiar
     
    Battleax, Sep 29, 2005
    #3
  4. Nomen Nescio

    Tm Guest

    I would say KK is a jerk. The tip is a very useful one and quite correct.

    T
     
    Tm, Sep 30, 2005
    #4
  5. Nomen Nescio

    kriyamanna Guest

    Nomen Nescio was on his good behavior, trying to establish himself as
    an
    "expert" on Amal carburetors. In a few days, after he's established
    himself
    as knowledgeable, he'll start telling you how to do things that might
    wreck your engine, and he'll want to waste everybody's time debating
    the physics of two-wheeled vehicles.

    But, if you like him that much, why don't you invite him to
    alt.motorcycles.triumph and crown him king?
     
    kriyamanna, Sep 30, 2005
    #5
  6. The difference is that KK's posts reveal an in-depth understanding
    of motorcycle mechanics and engineering. NN is a prat who
    knows how, on occasion, to type stuff here that he reads elsewhere.

    Perhaps you've missed the entire corpus of NN's drivel? It's
    self-serving and inane.

    --
    "Well," Brahma said, "even after ten thousand explanations, a fool is no
    wiser, but an intelligent man requires only two thousand five hundred."
    - The Mahabharata

    Don't send me email replies -- this is a honeypot address for unsolicited
    commercial email.
     
    Michael Sierchio, Sep 30, 2005
    #6
  7. While Krusty is knowledgable, he's still a jerk.
     
    Michael J. Freeman, Sep 30, 2005
    #7
  8. But what's your point? I generally prefer my moto mechanic,
    my surgeon or the pilot of the plane I'm on to be competent --
    being nice is a distant second. Suffering fools gladly is
    never something I've thought to be a virtue.


    --
    "Well," Brahma said, "even after ten thousand explanations, a fool is no
    wiser, but an intelligent man requires only two thousand five hundred."
    - The Mahabharata

    Don't send me email replies -- this is a honeypot address for unsolicited
    commercial email.
     
    Michael Sierchio, Sep 30, 2005
    #8
  9. Whether the eponymous krusty kritter is an avatar or an atavism, he
    resolves to remain unconcerned with what most other people think of
    him...

    And that is the beginning of jerk liberation...

    Om mani padme---aw, stuff it!
     
    krusty kritter, Sep 30, 2005
    #9
  10. Nomen Nescio

    Tm Guest

    Perhaps.

    TM
     
    Tm, Oct 1, 2005
    #10
  11. One of the problems with "Nomen Nescio" is that he's using an anonymous
    remailer service where about 99.9% of all users are "Nomen Nescio". I
    found almost 200,000 posts on google, all from "Nomen Nescio" clones...

    Sometimes *two* Nomen Nescios will be posting to one newsgroup,
    confusing the other Usenet denizens as to what their agendas may be...

    However, some of us are fairly sure that *this* particular
    "Nomen Nescio's" agenda is to show us how smart he is, and he wants to
    turn this NG, which is basically about riders helping each other solve
    nuts and bolts problems, into a debating forum...

    And that just wastes the time of the knowledgeable people who actually
    can help the newbies with their problems.
     
    krusty kritter, Oct 1, 2005
    #11
  12. Nomen Nescio

    Tm Guest

    Fair enough, I withdraw my comment. It was good info though.

    TM
     
    Tm, Oct 1, 2005
    #12
  13. The older I get the more I realize no one is irreplaceable. There are
    plenty of competent *and* nice people out there. Why should I put up with
    jerky behavior?
     
    Michael J. Freeman, Oct 3, 2005
    #13
  14. What, is somebody *forcing* you to read krusty kritter's helpful advice
    to newbies and his occasional abrasive remarks to trolls?

    No, you're posting to newsgroups out of boredom and loneliness instead
    of getting out and interacting with real live human beans.

    It's easy to stop your compulsive behavior, once you realize that it's
    compulsive. Surfing the web out of boredom instead of going for a brisk
    walk or an aerobic bicycle ride is as compulsive as stuffing a
    cheeseburger in your face when you're not hungry.
     
    krusty kritter, Oct 3, 2005
    #14
  15. What, is somebody *forcing* you to read krusty kritter's helpful advice
    to newbies and his occasional abrasive remarks to trolls?

    No, you're posting to newsgroups out of boredom and loneliness instead
    of getting out and interacting with real live human beans.

    It's easy to stop your compulsive behavior, once you realize that it's
    compulsive. Surfing the web out of boredom instead of going for a brisk
    walk or an aerobic bicycle ride is as compulsive as stuffing a
    cheeseburger in your face when you're not hungry.
     
    krusty kritter, Oct 3, 2005
    #15
  16. I can't help myself! I always pause when I see signs of intelligent
    life. If others don't appreciate your grandmotherly kindness, well --
    Soylent Green is... people!
     
    Michael Sierchio, Oct 4, 2005
    #16
  17. I haven't viewed "Soylent Green" in many years, but my coworker at a
    wastewater treatment plant in Los Angeles said that the scenes of one
    of the characters swimming to keep fit were filmed in an aeration tank
    there.

    Aeration is one of the final wastewater treatment stages, there isn't
    any solid material floating in the water by that point.

    I suppose they shut off the aeration while the actor (or his body
    double) was swimming, since it's very hard to swim in aerated water.
    And it smells pretty bad, too.

    And, when I get into flame wars with various Usenet trolls, I often
    think of the movie where Beau Bridges made a living as a cesspool
    diver. He would show up at a redneck house in hillbilly country wearing
    an immaculate white suit and announce that he would jump in their
    cesspool for fifty cents.

    The bored rednecks would often figure that such a spectacle was worth
    fifty cents and Beau Bridges would collect the money, put on his diving
    googles and jump into the cesspool and swim around for five minutes,
    then the rednecks would haul him out, and he'd go sit on their porch
    with them for half an hour talking to them and stinking up the porch.

    Then the rednecks would become annoyed and they'd ask why he didn't
    leave after collecting his fifty cents and doing his cesspool dive.

    And Beau Bridges would say, "For fifty dollars, I will leave."

    Anybody doesn't like krusty kritter's style can always set up a PayPal
    account and mail me $50.00 and I'll stop stinking up the place---at
    least long enough to burn up $50.00 worth of gas in my Yamahahahaha...

    Never thought I'd be hoping for $2.00 a gallon gasoline.
     
    krusty kritter, Oct 4, 2005
    #17
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